Micro-electromechanical (MEM) devices having mirrors therein have been proposed for directing optical beams across an optoelectronic substrate. Such devices are useful in a wide variety of applications ranging from displays to photonic NxN switches. Such devices are disclosed in U.S. Pat. No. 5,903,380 to Motamedi et al. entitled “Micro-Electromechanical (MEM) Optical Resonator and Method”. In particular, the '380 patent to Motamedi et al. discloses an integrated micro-electromechanical optical resonator that comprises a cantilever beam which is fixed to a substrate at one end and extends freely over the substrate at the other end. A bimorph actuator is also provided and is stacked on top of the beam at its fixed end. A reflective surface also partially covers the top of the beam at its free end. The bimorph actuator comprises material layers having different thermal expansion coefficients. A DC-biased AC voltage connected across the actuator causes it to heat and cool as the current passing through it increases and decreases. This creates a thermal bimorph effect which causes the cantilever beam and the reflective surface to oscillate in accordance with the varying current. Combining the resonator with a light source and actuator excitation circuitry creates an optical scanner engine which delivers a scan angle in excess of 20 degrees and a high scan rate. Unfortunately, the mirror surface provided on the cantilever beam of the '380 patent may not have near diffraction-limited optical quality because the cantilever beam may become warped or otherwise distorted in response to the bimorph effect.
U.S. Pat. No. 5,867,302 to Fleming entitled “Bistable Micro-electromechanical Actuator” also discloses a MEM device having mirrors therein. In particular, the '302 patent discloses a MEM actuator that is formed on a substrate and includes a stressed membrane of generally rectangular shape that upon release assumes a curvilinear cross-sectional shape due to attachment at a midpoint to a resilient member and at opposing edges to a pair of elongate supports. The stressed membrane can be electrostatically switched between a pair of mechanical states having mirror-image symmetry, with the MEM actuator remaining in a quiescent state after a programming voltage is removed. The bistable MEM actuator according to various embodiments of the present invention can be used to form a nonvolatile memory element, an optical modulator (with a pair of mirrors supported above the membrane and moving in synchronism as the membrane is switched), a switchable mirror (with a single mirror supported above the membrane at the midpoint thereof) and a latching relay (with a pair of contacts that open and close as the membrane is switched). Arrays of bistable MEM actuators can also be formed for applications including nonvolatile memories, optical displays and optical computing. FIGS. 7a-7b of the '302 patent also disclose an embodiment of the MEM actuator that includes a rotatable mirror. Unfortunately, the process described in the '302 patent for forming a membrane upon which the rotatable mirror is supported is relatively complicated and may not be suitable with conventional microelectronic processing techniques. Thus, the devices disclosed in the '302 patent may not be readily integrated with electronic devices on conventional integrated circuit substrates.
Thus, notwithstanding the above-described MEM devices having mirrors therein, there continues to be a need for optoelectronic devices that can redirect optical beams and have near diffraction-limited optical quality and methods of forming and operating same that are compatible with conventional microelectronic device fabrication techniques.